Added tests for pe_tw
Made setter/getter for time_stamp

Will now check for numerical string with 4 digits. It is a string
because it is used to determine the path and filename.
Renamed to fit better with different file formats.
ignore Tests/Test_resources/ folder

contains a lot of data
pe_merge will now merge correctly

It will now divide by the number of scans
n_scans moved up to DataClass
ignore pickles
ignore more pickles
test.py is now example script
Oh bloody hell, WTF with the pickles?
test.py is actually the script
ignore temp/test.pickle